The vaccine instructs a person's cells to make proteins associated with the coronavirus without making the person sick. Researchers hope the body's immune system will then kick in, creating the antibodies needed to fight off COVID-19.

"Messenger RNA is something the body produces on its own normally," said Mark Mulligan, chief of infectious diseases at NYU Langone Health. "It's kind of a new thing, but it's really not anything that's too different from what the body does for itself."

But Dr. Peter Hotez, co-director of the Texas Children's Center for Vaccine Development at Baylor University, said no RNA vaccine has been licensed because they have worked well only in laboratory animals.

"Those immune responses have not translated into ... good human immune responses," he said.

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Mulligan said he is optimistic about a trial underway at NYU, but he added that "the data will speak for itself."

"This is the science," he said. "You don't have to have faith or belief. The answer will come from the investigations that we do."

The vaccine is one of dozens under review in the global fight against the pandemic.